In an example of a laser printer, a developing cartridge is mounted in an apparatus body. Toner is accommodated in the developing cartridge. The toner in the developing cartridge is used to form an image on sheet. If there is no toner in the developing cartridge, the developing cartridge is removed from the apparatus body and a new developing cartridge is mounted in the apparatus body. Further, when sheet jam occurs in the apparatus body, the developing cartridge is removed from the apparatus body. And, after the sheet jam is solved, the developing cartridge is mounted again in the apparatus body.
In order to determine the service life of the developing cartridge, a technique for determining whether the developing cartridge mounted in the apparatus body is a new product or an old product has been proposed.
A detecting gear is provided to a side surface of the developing cartridge. The detecting gear is configured to rotate about an axis (rotational axis) extending in a direction perpendicular to the side surface. The detecting gear includes a plate-shaped detecting gear body and an abutting protrusion integrally formed with the detecting gear body. Herein, the abutting protrusion is provided outside (an opposite side of the developing cartridge's side surface relative to the detecting gear body) of the detecting gear body. The detecting gear body is provided with gear teeth over a partial peripheral surface thereof.
Further, a transmitting gear is provided to the side surface of the developing cartridge. The transmitting gear is configured to rotate about an axis extending parallel to and spaced apart from the axis of the detecting gear. The transmitting gear is integrally rotated together with an agitator for agitating the toner in the developing cartridge. The transmitting gear includes gear teeth over an entire peripheral surface thereof.
In a new developing cartridge, the gear teeth of the transmitting gear is engaged with the gear teeth of the detecting gear. When the developing cartridge is mounted in the apparatus body, a driving force of the motor is inputted to the transmitting gear and then transmitted from the transmitting gear to the detecting gear owing to the engagement between the gear teeth of the transmitting gear and the gear teeth of the detecting gear.
Therefore, the detecting gear rotates and the abutting protrusion moves in a rotational direction of the detecting gear in accordance with the rotation of the detecting gear. When the detecting gear is continuously rotated and a part of the detecting gear without teeth is opposed to the gear teeth of the transmitting gear, the engagement between the gear teeth of the transmitting gear and the gear teeth of the detecting gear is released and thus the detecting gear stops rotating. Accordingly, when the developing cartridge has been mounted in the apparatus body at least once, the engagement between the gear teeth of the transmitting gear and the gear teeth of the detecting gear is released and this state is maintained.
A sensor for detecting passing of the abutting protrusion as a detected protrusion is provided in the apparatus body. It is determined whether the developing cartridge is a new product or an old product, based on the detecting result of the sensor. That is, when the developing cartridge is mounted in the apparatus body and then the sensor detects the passing of the abutting protrusion, it is determined that the developing cartridge is a new product. On the contrary, when the developing cartridge is mounted in the apparatus body and then the sensor does not detect the passing of the abutting protrusion, it is determined that the developing cartridge is an old product (Refer to, for example, JP-A-2006-267994).